There is no need to take steroids at 18. If you only put on a couple of pounds in a year then there must be something amiss in something your doing or not doing.
Please post your training routine and weights being lifted. Please be honest, because I truely feel this may help slam on 10-15 maybe 20-25lbs if you get things right. Steroids are a last resort for someone above the age of 21 at least. Personally my view is 25 years old at least.
Anyway, please post your weekly routine and diet, the hours you sleep and the weights you lift and we'll go from there.